The objective of this research work is to gain a better understanding of the molecular mechanism involved in protein synthesis initiation in red blood cells. Specific research goals are: (1) Purification of peptide chain initiation factors from rabbit reticulocytes. Preparation of antibodies against purified factors. Studies of the effects of the antibodies in protein synthesis. (2) Development of radio-immune assays for peptide chain initiation factors and determination of the changes in factor activities under different physiological conditions. (3) Studies of the regulation of protein systhesis initiation in eukaryotic cells by eIF-2 kinases such as HRI and dsI.